1. Field of the Invention
This invention relates to a video signal editing apparatus such as VTR and more particularly to a video signal editing apparatus capable for providing for insertion-edition such that new video signals can be recorded in a desired position on the magnetic recording medium on which other video signals are previously recorded.
2. Description of the Prior Art
In editing video signals on a video tape recorder (VTR), it becomes necessary to perform a so-called insertion-editing in which the pattern of the video and control signals previously recorded on the video tape or other recording medium, which is the so-called base pattern, is partially rewritten or replaced by new video signals. When performing the insertion-editing, the video signals on the tape start to be reproduced at a standard speed at a position tens or hundreds of frames ahead of the editing start point or so-called in-point and the servo data prevailing at the time immediately preceding the aforementioned in-point, such as, for example, tape skew or drum rotation phase data and, for performing dynamic tracking, head displacement data are stored. These servo data are utilized for controlling dynamic tracking servo, drum servo or capstan servo in the course of the insertion-editing for achieving coincidence of the tape skew and recording video phase between the base pattern and the newly insertion-edited pattern.
However, when performing the insertion-editing over a number of times on end, servo data discontinuities may be caused frequently at the point of returning to the base pattern, that is, ahead and back of the final editing end point or out-point, thus resulting in markedly disturbed playback image. In extreme cases, servo data discontinuities are so pronounced that it becomes impossible to perform servo control and hence the electronic editing operation can not be performed.
For example, when producing animation tapes, that is, tapes containing animation scenes, for example, it becomes necessary to perform a continuous editing consisting of a large number of individual editing operations in which a plurality of small shots each consisting of up to 20 frames are continuously insertion-recorded a number of times. At this time, since the in-point servo data for any arbitrary intermediate insertion-editing operation is obtained upon reproducing the immediately preceding insertion-edited pattern, servo data detection error and servo control error are accumulated with the increase in the number of times the editing is performed, with the result that servo data continuity is affected at the time of returning to the original base pattern at the out-point of the final insertion-editing thus causing so-called transients in the signal pattern. Therefore, at the time of the preview operation after the end of editing, reproduced images are disturbed in the vicinity of the editing end point or out-point so that it becomes necessary to again perform the editing operation. The result is the unavoidably lowered editing efficiency or image quality.